Search results for "osso"
showing 10 items of 801 documents
Disturbed Exploitation compact Differential Evolution for Limited Memory Optimization Problems
2011
This paper proposes a novel and unconventional Memetic Computing approach for solving continuous optimization problems characterized by memory limitations. The proposed algorithm, unlike employing an explorative evolutionary framework and a set of local search algorithms, employs multiple exploitative search within the main framework and performs a multiple step global search by means of a randomized perturbation of the virtual population corresponding to a periodical randomization of the search for the exploitative operators. The proposed Memetic Computing approach is based on a populationless (compact) evolutionary framework which, instead of processing a population of solutions, handles …
Cooperative Spin Transition in the Two-Dimensional Coordination Polymer [Fe(4,4′-bipyridine)2(NCX)2]·4CHCl3 (X = S, Se)
2011
Two new isostructural two-dimensional (2D) coordination polymers exhibiting spin crossover (SCO) behavior of formulation [Fe(4,4'-bipy)(2)(NCX)(2)]·4CHCl(3) (4,4'-bipy = 4,4'-bipyridine; X = S [1·4CHCl(3)], Se [2·4CHCl(3)]) have been synthesized and characterized, and both undergo cooperative spin transitions (ST). For 1·4CHCl(3) the ST takes place in two steps with critical temperatures of T(c1)(down) = 143.1 K, T(c2)(down) = 91.2 K, T(c1)(up) = 150.7 K, and T(c2)(up) = 112.2 K. 2·4CHCl(3) displays half ST characterized by T(c)(down) = 161.7 K and T(c)(up) = 168.3 K. The average enthalpy and entropy variations and cooperativity parameters associated with the ST have been estimated to be ΔH…
Spin Crossover Iron(II) Coordination Polymer Chains: Syntheses, Structures, and Magnetic Characterizations of [Fe(aqin) 2 (μ 2 -M(CN) 4 )] (M = Ni(II…
2014
International audience; New Fe(II) coordination polymeric neutral chains of formula [Fe(aqin)2(μ2-M(CN)4)] (M = NiII (1) and PtII (2)) (aqin = Quinolin-8-amine) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction, and magnetic measurements. The crystal structure determinations of 1–2 reveal in both cases a one-dimensional structure in which the planar [M(CN)4]2– (M = NiII (1) and PtII (2)) anion acts as a μ2-bridging ligand, and the two aqin molecules as chelating coligands. Examination of the intermolecular contacts in the two compounds reveals that the main contacts are ascribed to hydrogen bonding interactions involving the amine groups of the aqin chelati…
Thermal-, pressure- and light-induced spin-crossover behviour in the two-dimensional Hofman-like coordination polymer [Fe(3-Clpy)2Pd(CN)4]
2013
The thermal spin-crossover behaviour, photoexcitation and subsequent relaxation, as well as the pressure-induced spincrossover behaviour at 298 K are discussed for the non-porous two-dimensional Hofmann-like coordination polymer [Fe(3-Clpy)(2)Pd(CN)(4)] (1). The title compound undergoes a two-step, cooperative thermal-induced SCO with critical temperatures T-c1(down arrow) = 159.6 K and T-c1(up arrow) = 164.5 K for the first step and T-c2(down arrow) = 141.4 K and T-c2(up arrow) = 148.4 K for the second step. Irradiation of the low-spin state with green light (514 nm) at 10 K induced the photoexcitation of around 60% of the iron(II) centres to the high-spin state (LIESST effect). The subseq…
Fast detection of water and organic molecules by a change of color in an iron(II) microporous spin-crossover coordination polymer.
2012
Here we present a novel three-dimensional iron(II) spin-crossover porous coordination polymer based on the bis(1,2,4-triazol-4-yl)adamantane (tr(2)ad) ligand and the [Au(CN)(2)](-) metalloligand anions with the formula {Fe(3)(tr(2)ad)(4)[Au(CN)(2))](2)}[Au(CN)(2)](4)·G. The sorption/desorption of guest molecules, water, and five/six-membered-ring organic molecules is easily detectable because the guest-free and -loaded frameworks present drastically distinct coloration and spin-state configurations.
Macrocycle-Based Spin-Crossover Materials
2009
International audience; New iron(II) complexes of formula [Fe(L1)](BF(4))(2) (1) and [Fe(L2)](BF(4))(2) x H(2)O (2) (L1 = 1,7-bis(2'-pyridylmethyl)-1,4,7,10-tetraazacyclododecane; L2 = 1,8-bis(2'-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane) have been synthesized and characterized by infrared spectroscopy, variable-temperature single-crystal X-ray diffraction, and variable-temperature magnetic susceptibility measurements. The crystal structure determinations of 1 and 2 reveal in both cases discrete iron(II) monomeric structures in which the two functionalized tetraazamacrocycles (L1 and L2) act as hexadentate ligands; the iron(II) ions are coordinated with six nitrogen atoms: four from …
Cyanocarbanion-based spin-crossover materials: photocrystallographic and photomagnetic studies of a new iron(II) neutral chain
2010
International audience; A new iron(II) chain of formula [Fe(abpt)(2)(tcpd)] [1; (tcpd)(2-) = [C(10)N(6)](2-) = (C[C(CN)(2)](3))(2-) = 2-dicyanomethylene-1,1,3,3-tetracyanopropanediide anion, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole] has been synthesized and characterized by IR spectroscopy, detailed variable-temperature single-crystal X-ray diffraction, magnetic and photomagnetic measurements. The crystal structure determination of 1 reveals a one-dimensional structural architecture in which the (tcpd)(2-) cyanocarbanion acts as a μ(2)-bridging ligand and the two abpt molecules act as chelating ligands. Detailed X-ray diffraction studies as a function of the temperature (293-10 K…
A Two-State Computational Investigation of Methane C-H and Ethane C-C Oxidative Addition to [CpM(PH3)]n+ (M=Co, Rh, Ir;n=0, 1)
2006
Reductive elimination of methane from methyl hydride half-sandwich phosphane complexes of the Group 9 metals has been investigated by DFT calculations on the model system [CpM(PH(3))(CH(3))(H)] (M = Co, Rh, Ir). For each metal, the unsaturated product has a triplet ground state; thus, spin crossover occurs during the reaction. All relevant stationary points on the two potential energy surfaces (PES) and the minimum energy crossing point (MECP) were optimized. Spin crossover occurs very near the sigma-CH(4) complex local minimum for the Co system, whereas the heavier Rh and Ir systems remain in the singlet state until the CH(4) molecule is almost completely expelled from the metal coordinati…
Crystal structure of the coordination polymer [FeIII2{PtII(CN)4}3]
2015
[EN] The title complex, poly[dodeca--cyanido-diiron(III)triplatinum(II)], [FeIII2{PtII(CN)4}3], has a three-dimensional polymeric structure. It is built-up from square-planar [PtII(CN)4] 2 anions (point group symmetry 2/m) bridging cationic [FeIIIPtII(CN)4] + 1 layers extending in the bc plane. The FeII atoms of the layers are located on inversion centres and exhibit an octahedral coordination sphere defined by six N atoms of cyanide ligands, while the PtII atoms are located on twofold rotation axes and are surrounded by four C atoms of the cyanide ligands in a square-planar coordination. The geometrical preferences of the two cations for octahedral and square-planar coordination, respectiv…
Vibrational properties of 1D- and 3D polynuclear spin crossover Fe(II) urea-triazoles polymer chains and quantification of intrachain cooperativity
2020
Abstract The vibrational dynamics of the iron centres in 1D and 3D spin crossover Fe(II) 4-alkyl-urea triazole chains have been investigated by synchrotron based nuclear inelastic scattering. For the 1D system, the partial density of phonon states has been modelled with density functional theory methods. Furthermore, spin dependent iron ligand distances and vibrational modes were obtained. The previously introduced intramolecular cooperativity parameter H coop (Rackwitz et al, Phys. Chem. Chem. Phys. 2013, 15, 15450) has been determined to −31 kJ mol−1 for [Fe(n-Prtrzu)3(tosylate)2] and to +27 kJ mol−1 for [Fe(n-Prtrzu)3(BF4)2]. The change of sign in H coop is in line with the incomplete an…